如何学习C语言、入门C语言，看这篇就够了

莫愁
C语言
2019-11-10

简介该文章将会把C语言基础语法梳理一遍,主要记录帮助理解相关知识点的代码示例和重要或容易忽略的面试知识,将会陆续发布系类文章.
字数 24775

数据类型与操作符

1. 程序1:计算圆面积时使用常量pi

/*本程序演示const关键词*/
   #define PI 3.14159  /* 声明常量PI*/
   #include <stdio.h>
   void main(int argc, char const *argv[])
   {
       float radius,area;
       printf("\n Entre radius: ");
       scanf("%f",&radius);
       area = PI*radius*radius;
       printf("\nArea of circle: %f",area);
       return 0;
   }

另外一种方式定义常量是使用预处理宏定义命令‘#define’,好处是常量不占用内存.示例代码为:

#define PI 3.14159  /* 声明常量PI*/
#include <stdio.h>
void main(int argc, char const *argv[])
{
    float radius,area;
    printf("\n Entre radius: ");
    scanf("%f",&radius);
    area = PI*radius*radius;
    printf("\nArea of circle: %f",area);
    return 0;
}

程序3 操作符

1.算数操作符(+,—,*,/,%);
2.赋值(=);
3.一元操作符(- 一元减法操作符,–,++);
4.三元操作符(?:);
5.关系操作符(<,<=,>,>=,==,!=);
6.逻辑操作符(&&,||,!);
7.位操作符(~,&,|,^, <<,>>)

/* 理解各种操作符*/
#include <stdio.h>
void main(int argc, char const *argv[])
{
    int x,y;
    /* 将数字10,12分别保存至变量雄,x,y中*/
    x = 10;
    y = 12;
    printf("\nn~x = %d",(~x));
    printf("\nx&y = %d",(x&y));
    printf("\nx|y = %d",(x|y));
    printf("\nx^y = %d",(x^y));
    printf("\nx<<2 = %d",(x<<y));
    printf("\nx>>2 = %d"(x>>2));
    return 0;
}

程序4 sizeof()操作符

/* 了解如何使用sizeof()操作符*/
#include<stdio.h>
void main()(int argc, char const *argv[])
{
    int a;
    long int b;
    printf("\nsize of a = %d",sizeof(a));
    printf("\nsize of b = %d",sizeof(b));
    printf("\nsize of int = %d",sizeof(int));
    printf("\nsize of long int = %d",sizeof(long));
    return 0;
}

输出:

size of a = 2
size of b = 4
size of int = 2
size of long int = 4

程序5 取地址操作符&

/* 获取变量x的十六进制的内存地址*/
#include<stdio.h>
void main(int argc, char const *argv[])
{
    int x;
    printf("Memory address = %x", &x);
    return 0;
}

输出为:

Memory address = fff4

程序6 指针操作符

/* 获取变量的内存地址*/
#include<stdio.h>
void main(int argc, char const *argv[])
{
    int x = 100;
    int *p; // 声明指针变量
    p = &x; // 将变量x的地址保存到p中
    // p代表变量x的内存地址
    printf("Memory address = %x",p);
    // *p代表变量x的值
    printf("\nPointer refers to %d",*p);
    return 0;
}

输出:

Memory address = fff4
Pointer refers to 100

程序7 操作符优先级

示例代码1:

/* 用来演示两个整数相除,结果仍然为整数*/
#include<stdio.h>
void main(int argc, char const *argv[])
{
    int x = 3,y = 2;
    float z = x/y;
    printf("\n Result of division = %f",z);
    return 0;
}

输出:

Result of division = 1.000000

示例代码2:
两个整数相除时使用类型转换

#include<stdio.h>
void main(int argc, char const *argv[])
{
    int x = 3,y = 2;
    float z = (float)x/y;
    printf("\n Result of division = %f",z);
    return 0;
}

输出: